Beta Diversity of Plant-Pollinator Interactions in Anthropogenic Landscapes

Data are of plant-pollinator interactions from twenty-one sites in the Dublin region of Ireland (Figure 1) sampled four times between 5 May and 20 August 2018
at monthly intervals. Plants and pollinators were sampled along a 2m x 1km
transect within each 1.5km radius site, with sub-sections of the transect
allocated proportionately to all land cover types comprising more than 1% of
the selected site (e.g. pasture, arable, continuous urban fabric; see Figure S1 Legend). Transects in residential areas were positioned along the boundary
between pavements and residential gardens, so that 1m of the transect width was
located in gardens and the other 1m was located on pavements and road verges. Transect
locations were chosen using a random number generator to select points, and
transect sections were located as close as possible to those points. Where land
cover types were particularly dominant within a site, a maximum transect
section length of 250m was walked, with multiple transects of the same land
cover walked across multiple locations.

Flowers
were sampled by noting every flowering species on the outward walk of the
transect and then counting the floral units of each species on the return walk.
A floral unit was defined as an individual flower or collection of flowers that
an insect of 5 mm body length could walk between (see Baldock et al. 2015,
Supplementary Material Table S4) and comprised a single capitulum for
Asteraceae, a secondary umbel for Apiaceae and a single flower for most other
taxa. Grasses, sedges and wind-pollinated forbs were not sampled.

Flower-visitor
interactions were quantified by walking along each transect and recording every
insect on flowers up to 1m either side of the transect line to a height of 2m,
where appropriate, e.g. along hedgerows. An attempt was made to net all bees
and hoverflies (Syrphidae), which were frozen and later identified to species.
All other flower visiting insects were recorded at the family level
(Coleoptera, Diptera, Lepidoptera). Bees and hoverflies were identified using
Falk (2015) and Stubbs & Falk (2002) respectively, with identifications
checked by taxonomists (See Acknowledgements). Plants were identified using
Rose & O’Reilly (2006) and the phone application Plantnet (available at: https://identify.plantnet-project.org/), 85% to species and the rest to
genus or morpho species. Sampling for flower visitors and their interactions
took place between 09:00 and 19:00 hours on dry, warm, non-windy days.